Plasma Display Panel Driving Method and Plasma Display Device

ABSTRACT

A PDP driving method. A falling ramp voltage is applied to a scan electrode so as to reset a state of wall charges of a discharge cell during a reset period. In this instance, a sustain electrode is maintained at a high voltage during an initial period for applying the falling ramp voltage, and the voltage at the sustain electrode is reduced to a normal voltage at a latter part of the period for applying the falling ramp voltage. Accordingly, the voltage applied to an address electrode is reduced in an address period since an erased amount of the wall charges of the address electrode is reduced during the reset period.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/936,014, filed on Sep. 8, 2004, which claims priority to and thebenefit of Korea Patent Application Nos. 2003-63134 and 2003-76979 filedon Sep. 9, 2003 and Oct. 31, 2003, respectively, in the KoreanIntellectual Property Office, the entire contents of both of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a PDP (plasma display panel) drivingmethod and a plasma display device.

(b) Description of the Related Art

A PDP is a flat display for showing characters or images using plasmagenerated by gas discharge. PDPs can include pixels numbering more thanseveral million in a matrix format, in which the number of pixels aredetermined by the size of the PDP. Referring to FIGS. 1 and 2, a PDPstructure will now be described.

FIG. 1 shows a partial perspective view of the PDP, and FIG. 2schematically shows an electrode arrangement of the PDP.

As shown in FIG. 1, the PDP includes glass substrates 1 and 6 facingeach other with a predetermined gap therebetween. Scan electrodes 4 andsustain electrodes 5 in pairs are formed in parallel on glass substrate1, and scan electrodes 4 and sustain electrodes 5 are covered withdielectric layer 2 and protection film 3. A plurality of addresselectrodes 8 is formed on glass substrate 6, and address electrodes 8are covered with insulator layer 7. Barrier ribs 9 are formed oninsulator layer 7 between address electrodes 8, and phosphors 10 areformed on the surface of insulator layer 7 and between barrier ribs 9.Glass substrates 1 and 6 are provided facing each other with dischargespaces between glass substrates 1 and 6 so that scan electrodes 4 andsustain electrodes 5 can cross address electrodes 8. Discharge space 11between address electrode 8 and a crossing part of a pair of scanelectrode 4 and sustain electrode 5 forms discharge cell 12, which isschematically indicated.

As shown in FIG. 2, the electrodes of the PDP have an n×m matrix format.Address electrodes A₁ to A_(m) are arranged in the column (vertical)direction, and n scan electrodes Y₁ to Y_(n) and n sustain electrodes X₁to X_(n) are arranged in pairs in the row (horizontal) direction.Scan/sustain driving circuit 13 is coupled to scan electrodes Y₁ toY_(n) and sustain electrodes X₁ to X_(n), and address driving circuit 15is coupled to address electrodes A₁ to A_(m).

In the general PDP, a frame is divided into a plurality of subfields andthen driven, and gray scales are displayed by combination of thesubfields. Each subfield includes a reset period, an address period, anda sustain period. In the reset period, wall charges formed by a previoussustain discharging are erased, and wall charges are set up so as toperform a next stable address discharging. In the address period, cellswhich are turned on and cells which are not turned on are selected, andthe wall charges are accumulated on the turned-on cells (addressedcells). In the sustain period, a sustain discharging for displaying theactual image on the addressed cells is executed.

As shown in FIG. 3, the reset period includes a rising ramp period and afalling ramp period. In the rising ramp period, a ramp voltage graduallyrises to voltage V_(set) from voltage V_(s) while address electrode Aand sustain electrode X are maintained at 0V. While the ramp voltagerises, a weak reset discharging is generated to address electrode A andsustain electrode X from scan electrode Y in all the discharge cells. Asa result, negative wall charges are accumulated on scan electrode Y, andpositive wall charges are accumulated on address electrode A and sustainelectrode X. More accurately, the wall charges are accumulated onprotection film 3 which covers scan electrode Y and sustain electrode Xand on insulator layer 7 which covers address electrode A. For ease ofdescription, the wall charges are described to be accumulated on scanelectrode Y, sustain electrode X, and address electrode A.

A ramp voltage which gradually falls to 0V from voltage V_(s) is appliedto scan electrode Y while sustain electrode X is maintained at voltageV_(e) in the falling ramp period. While the ramp voltage falls, a weakreset discharging is generated in all the discharge cells. As a result,the negative wall charges on scan electrode Y are reduced, and thepositive wall charges on sustain electrode X and address electrode A arereduced.

In this instance, it is required that a high voltage be applied toaddress electrode A for the address discharging during the addressperiod since a large amount of charges are erased from among thepositive wall charges accumulated on address electrode A according tothe conventional waveform. That is, a switch having a high withstandvoltage needs to be used by a circuit applying a voltage to addresselectrode A, and power consumption is also increased because of the highvoltage.

SUMMARY OF THE INVENTION

In accordance with the present invention a PDP driving method isprovided for generating address discharging by using a low voltage.

In the present invention, the voltage applied to the sustain voltage isincreased during a partial latter part of the reset period.

In one aspect of the present invention, a method is provided for drivinga PDP which includes a plurality of first and second electrodes formedin parallel, and a plurality of third electrodes which cross the firstand second electrode. The adjacent first electrode, the secondelectrode, and the address electrode form a discharge cell. A voltage atthe first electrode is gradually reduced to a second voltage in a resetperiod. A third voltage and a fourth voltage are respectively applied tothe first electrode and the third electrode of the discharge cell to beselected from among the discharge cells in an address period. The secondelectrode is maintained at a fifth voltage for a predetermined time, anda sixth voltage which is less than the fifth voltage is applied to thesecond electrode while the voltage at the first electrode falls to thesecond voltage from first voltage.

The sixth voltage is a voltage having the same level as that of thevoltage applied to the second electrode during the address period.

In addition, a seventh voltage greater than the sixth voltage is appliedto the second electrode during the address period, and the seventhvoltage is a voltage with the same level as that of the fifth voltage.

Also, the fifth voltage is a voltage with the same level as that of thevoltage applied for the sustain discharge to the second electrode duringthe sustain period.

The voltage applied to the second electrode is varied stepwise from thesixth voltage to the fifth voltage, or the second electrode is floatedand the fifth voltage is applied to the second electrode after thepredetermined time.

The voltage applied to the second electrode gradually falls from thesixth voltage to the fifth voltage. The gradient falling to the fifthvoltage from the sixth voltage corresponds to the gradient falling tothe second voltage from the first voltage.

The voltage at the first electrode gradually falls to the second voltagefrom the first voltage on at least one slope. The step of graduallyreducing a voltage at the first electrode to a second voltage from afirst voltage includes repeating a period for reducing the voltage atthe first electrode by a predetermined voltage and a period for floatingthe first electrode.

In another aspect of the present invention, a plasma display device isprovided which includes a plurality of first and second electrodesformed in parallel, and a plurality of third electrodes which cross thefirst and second electrodes; and a driving circuit for applying drivingsignals to the first, second, and third electrodes. The driving circuitgradually reduces a voltage at the first electrode to the second voltagefrom the first voltage, and modifies a voltage at the second electrodeto the fourth voltage from the third voltage while the voltage at thefirst electrode is varied to the second voltage from the first voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial brief perspective view diagram of a PDP.

FIG. 2 shows an electrode arrangement diagram of a PDP.

FIG. 3 shows a conventional PDP driving waveform diagram.

FIG. 4 shows a PDP driving waveform diagram according to a firstexemplary embodiment of the present invention.

FIG. 5 shows a diagram of a wall charge distribution caused by thewaveforms of FIGS. 3 and 4.

FIGS. 6 and 7 respectively show wall voltages caused by the drivingwaveforms of FIGS. 3 and 4, and the states of applied voltages.

FIGS. 8 to 11 respectively show PDP driving waveform diagrams accordingto second to fifth exemplary embodiments of the present invention.

FIG. 12A shows a diagram of modeled discharge cells formed by a sustainelectrode and a scan electrode.

FIG. 12B shows an equivalent circuit diagram of FIG. 12A.

FIG. 12C shows a state in which an external voltage is applied to thedischarge cells of FIG. 12A.

FIG. 12D shows a floated state of when the discharge cells aredischarged.

FIG. 13 shows a PDP driving waveform diagram according to a sixthexemplary embodiment of the present invention.

DETAILED DESCRIPTION

Referring now to FIG. 4, each subfield in the driving waveform accordingto the first exemplary embodiment of the present invention includesreset period P_(r), address period P_(a), and sustain period P_(s),reset period P_(r) includes erase period P_(r1), rising period P_(r2),and falling period P_(r3).

Erase period P_(r1) of reset period P_(r) is for erasing the chargesformed by a sustain discharging in sustain period P_(s) of a previoussubfield. Rising period P_(r2) is a period for forming wall charges onscan electrode Y, sustain electrode X, and address electrode A. Fallingperiod P_(r3) is a period for erasing part of the wall charges formed inrising period P_(r2) to thus support the address discharging. Addressperiod P_(a) is a period for selecting a discharge cell to be sustainedin the sustain period from among a plurality of discharge cells. Sustainperiod P_(s) is a period for alternately applying a sustain pulse toscan electrode Y and sustain electrode X to sustain-discharge thedischarge cell selected in address period P_(a).

Scan/sustain driving circuit 13 shown in FIG. 2 for applying a drivingvoltage to scan electrode Y and sustain electrode Y in respectiveperiods P_(r), P_(a), and P_(s), and address driving circuit 15 shown inFIG. 2 for applying a driving circuit to address electrode A are coupledto the PDP to thus configure a displaying device.

Still referring to FIG. 4, voltage V_(h) which is greater than voltageV_(e) by voltage V_(p) is applied to sustain electrode X during periodP_(r31) which corresponds to the initial part of falling period P_(r3),and voltage V_(e) is applied to sustain electrode X during second periodP_(r32) which corresponds to the latter part of falling period P_(r3) inthe driving waveform according to the first exemplary embodiment of thepresent invention. A ramp voltage which gradually falls to the referencevoltage from voltage V_(s) is applied to scan electrode Y. Theabove-noted ramp voltage falls with a predetermined gradient or with avariable gradient. Accordingly, a discharge is more quickly generatedduring falling period P_(r3) in the driving waveform of FIG. 4 comparedto the driving waveform of FIG. 3, and the erased amount of the wallcharges accumulated on address electrode A is reduced, which will bedescribed with reference to FIGS. 5 to 7.

First, in rising period P_(r2) of FIGS. 3 and 4, a ramp voltage whichgradually rises from voltage V_(s) to voltage V_(set) which is greaterthan a discharge firing voltage is applied to scan electrode Y, while 0Vis applied to sustain electrode X and address electrode A. A weakresetting is generated from scan electrode X to address electrode A andsustain electrode X while the ramp voltage rises, and as a result, thenegative wall charges are accumulated on scan electrode Y, and thepositive wall charges are concurrently accumulated on address electrodeA and sustain electrode X.

In this instance, since the potential of address electrode A has acharacteristic of maintaining a middle potential between scan electrodeY and sustain electrode X, the state of the wall charges at the end partof rising period P_(r2) is given as in FIG. 5. That is, the wall chargesthat correspond to the middle potential between the potential caused byvoltage V_(set) applied to scan electrode Y and the wall charges formedon scan electrode Y and the potential caused by 0V applied to sustainelectrode X and the wall charges formed on sustain electrode X areformed on address electrode A.

Next, the state of the wall charges during falling period P_(r3) of thedriving waveform according to the first exemplary embodiment will bedescribed with reference to FIGS. 6 and 7.

First, FIG. 6 shows an internal wall voltage when a ramp voltage whichfalls from voltage V_(s) to voltage V_(n) is applied to scan electrode Ywhile voltage V_(e) is applied to sustain electrode X in the like mannerof falling period P_(r3) of the driving waveform shown in FIG. 3. Asshown in FIG. 6, a voltage difference (referred to as an “appliedvoltage” hereinafter) between scan electrode Y caused by the externallyapplied voltage and sustain electrode X gradually falls from voltage(V_(s)-V_(e)) to voltage (V_(n)-V_(e)). When defining wall voltage V_(w)between scan electrode Y and sustain electrode X at the last point ofrising period P_(r2) of FIG. 3 as V_(w0), a discharge is generated whenthe voltage difference between voltage V_(w0) and applied voltage V_(in)becomes greater than discharge firing voltage V_(f). When a graduallyfalling ramp voltage is applied to generate a discharge, the wallvoltage within the discharge cell is reduced by the same gradient asthat of applied voltage V_(in). The above-described scheme is well-knownin the art as disclosed by U.S. Pat. No. 5,745,086, and hence, nodetailed description thereof will be provided.

Since voltage (V_(e)+V_(p)) is applied to sustain electrode X duringperiod P_(r31) of falling period P_(r3), and voltage V_(e) is applied tosustain electrode X during second period P_(r32) as shown in FIG. 4,applied voltage V_(in) gradually falls to voltage (V_(n)-V_(e)) fromvoltage (V_(s)-V_(e)-V_(p)) during first period P_(r31), and appliedvoltage V_(in) gradually falls to voltage (V_(n)-V_(e)) from voltage(V_(n)-V_(e)-V_(p)) during second period P_(r32). In this instance, whenthe difference between initial voltage V_(w0) of wall voltage V_(w) andapplied voltage V_(in) becomes greater than discharge firing voltageV_(f), a weak discharge occurs, and wall voltage V_(w) is reducedaccording to the same gradient as that of applied voltage V_(in). Sincethe difference between wall voltage V_(w) and applied voltage V_(in) isless than discharge firing voltage V_(f) during second period P_(r32), adischarge between sustain electrode X and scan electrode Y issuppressed.

Regarding FIGS. 6 and 7, a faster discharge is generated in fallingperiod P_(r3) in the driving waveform according to the first exemplaryembodiment of the present invention compared to the driving waveform ofFIG. 3. In this instance, the potentials of sustain electrode X and scanelectrode Y are higher than the driving waveform of FIG. 3 in theearlier part of falling period P_(r3). That is, the voltage externallyapplied to sustain electrode X is higher than the driving waveform ofFIG. 3 by voltage VP, and the voltage applied to scan electrode Y at thedischarge firing time is higher than the driving waveform of FIG. 3. Thepotentials of sustain electrode X and scan electrode Y in the drivingwaveform according to the first exemplary embodiment of the presentinvention are higher than the potential of the driving waveform of FIG.3 while the discharge is performed and applied voltage V_(in) falls withreference to the elapse time after the discharge is fired.

Therefore, the average potential of sustain electrode X and scanelectrode Y while a weak discharge is generated becomes higher than theaverage potential in the driving waveform of FIG. 3. Since the potentialof address electrode A has a characteristic of maintaining the averagepotential of sustain electrode X and scan electrode Y as describedabove, the potential of address electrode A is to be higher than thedriving waveform of FIG. 3. Since the voltage applied to the addresselectrode A in the driving waveforms of FIGS. 3 and 4 is the same, theamount of positive wall charges formed on address electrode A becomesgreater than the amount of wall charges in the driving waveform of FIG.3. That is, less of the positive wall charges accumulated on addresselectrode A are lost compared to FIG. 3.

In second period P_(r32) of falling period P_(r3), the voltage atsustain electrode X is reduced to voltage V_(e) again, and accordingly,the difference between wall voltage V_(w) and applied voltage V_(in) isreduced below discharge firing voltage V_(f), and the discharge betweenscan electrode Y and sustain electrode X is suppressed. In second periodP_(r32), a discharge between scan electrode Y and address electrode A isgenerated through priming particles generated by the discharge betweenscan electrode Y and sustain electrode X. That is, in the final part offalling period P_(r3), a weak discharge between scan electrode Y andaddress electrode A is actively generated while the discharge betweenscan electrode Y and sustain electrode X is suppressed, and hence, thewall voltage between scan electrode Y and address electrode A isprecisely controlled.

Loss of the positive wall charges formed on address electrode A isreduced, and the wall voltage between scan electrode Y and addresselectrode A is precisely controlled according to the first exemplaryembodiment. Accordingly, the wall voltage between address electrode Aand scan electrode Y is increased, and voltage V_(a) applied to addresselectrode A for selecting the discharge cell in address period P_(a) isreduced.

That is, voltage V_(n) is sequentially applied to scan electrode Y toselect scan electrode Y in address period P_(a) while another scanelectrode Y is maintained at voltage V_(sc). Address voltage V_(a) isapplied to address electrode A which forms a discharge cell to beselected from among the discharge cells formed by scan electrode Y towhich voltage V_(n) is applied. Accordingly, the address discharging isexecuted because of the difference between voltage V_(a) applied toaddress electrode A and voltage V_(n) applied to scan electrode Y andthe wall voltage caused by the wall charges formed on address electrodeA and scan electrode Y. In this instance, voltage V_(a) is reduced sincea large amount of positive wall charges are formed on address electrodeA, and the wall voltage is high.

Next, a sustain pulse is sequentially applied to scan electrode Y andsustain electrode X during sustain period P_(s). The sustain pulsefunctions so that the voltage difference between scan electrode Y andsustain electrode X may alternately be voltages V_(s,)-V_(s). VoltageV_(s) is less than the discharge firing voltage between scan electrode Yand sustain electrode X. When the wall voltage is formed between scanelectrode Y and sustain electrode X because of the address dischargingduring address period P_(a), a discharge is generated on scan electrodeY and sustain electrode X because of the wall voltage and voltage V_(s).The voltage pattern of sustain electrode X is modified from voltage Vhto voltage Ve in the step pattern as shown in FIG. 4, and in addition,the voltage pattern can be varied, which will now be described withreference to FIGS. 8 and 9.

FIGS. 8 and 9 respectively show PDP driving waveform diagrams accordingto second and third exemplary embodiments of the present invention.

Referring to FIG. 8, the voltage applied to sustain electrode X duringsecond period P_(r32) of falling period P_(r3) gradually falls tovoltage V_(e) from voltage V_(h). In this instance, the gradient of thevoltage applied to sustain electrode X is established to be equal to orsteeper than the gradient of the voltage applied to scan electrode Y.

When the voltage of sustain electrode X in the ramp format fallsgradually, the influence applied by the voltage variation of sustainelectrode X to the voltage variation of scan electrode Y is reducedsince the voltage is varied by a low-level current. That is, since ageneral ramp voltage generation circuit is realized to supply alow-level current, when the voltage at sustain electrode X is abruptlyvaried while transforming the voltage of scan electrode Y into a ramppattern, the current is not appropriately supplied to scan electrode Yin the ramp operation, and hence, the voltage of scan electrode Y can beinstantly influenced by the voltage variation of sustain electrode X.However, when the waveform of sustain electrode X is varied in the ramppattern as shown in FIG. 8, the voltage of scan electrode Y may not beinfluenced by the voltage variation of sustain electrode X since a lowcurrent is required for the voltage variation.

Referring to FIG. 9, voltage V_(e) is applied to sustain electrode Xwhen sustain electrode X is floated for a specific time during secondperiod P_(r32) of falling period P_(r3). As a result, a falling ramp isapplied to scan electrode Y. Sustain electrode X, which is floated whilethe current flows, fails to receive the current, and hence, thepotential of sustain electrode X follows the potential variation of scanelectrode Y. Therefore, the waveform of sustain electrode X can bemodified to the ramp pattern without a circuit for applying a rampvoltage to sustain electrode X, and hence, the bias of sustain electrodeX can be varied without influencing the ramp voltage applied to scanelectrode Y.

The waveforms which apply the falling ramp waveform after applying therising ramp waveform during the reset period have been described in thefirst exemplary embodiment of the present invention, and differing fromthis, it is also possible that the driving waveform applies a risingramp voltage and a falling ramp voltage during a main reset period andapplies a falling ramp voltage during a sub reset period, which will bedescribed in detail with reference to FIG. 10.

FIG. 10 shows a PDP driving waveform diagram according to the fourthexemplary embodiment of the present invention.

As shown, main reset period P_(r) _(—) _(main) is formed in the firstsubfield, and sub reset period P_(r-sub) is formed in a subsequentsubfield from among a plurality of subfields which configure a frame inthe driving waveform according to the fourth exemplary embodiment.

A rising ramp waveform is applied, and a falling ramp waveform is thenapplied in main reset period P_(r) _(—) _(main) which is the resetperiod of the first subfield. A falling ramp waveform is only applied insub reset period P_(r) _(—) _(sub) which is the reset period of thesubfield which is after the second subfield.

In general, a rising ramp waveform is applied to scan electrode Y so asto form a large amount of the wall charges on the discharge cell duringthe reset period. It is not needed to form the wall charges during thereset period in the subfield after the second subfield since a largeamount of wall charges are already formed on the discharge cell, whichemit light during the sustain period of the previous subfield, by thesustain discharging. Also, since no state of the wall charges formedduring the reset period is varied in the discharge cell which did notemit light during the sustain period, no reset operation is required tobe executed in the next subfield. The discharge cell maintains the resetstate since no discharge occurs if only a falling ramp waveform isapplied to scan electrode Y in this state.

In the last subfield, the wall charges formed by the sustain dischargingare erased by applying the waveform which corresponds to the waveformapplied in erase period P_(r1) of FIG. 4 to sustain electrode X, andaccordingly, the discharge cell is reset again in main reset periodP_(r-main) of the first subfield of a next frame. Main reset periodP_(r-main) is provided in the first subfield with reference to a framein the fourth exemplary embodiment, and in addition to this, main resetperiod P_(r-main) may be provided in another subfield.

As shown in FIG. 10, when a falling ramp voltage is applied to scanelectrode Y from main reset period P_(r-main) and sub reset period P_(r)_(—) _(sub) as shown in FIG. 10, voltage V_(h) is applied to sustainelectrode X during first period P_(r31), and voltage V_(e) is applied tosustain electrode X during second period P_(r32), and hence, a furtheramount of the wall charges are accumulated on address electrode A asdescribed above, and the voltage applied to address electrode A duringaddress period P_(a) is reduced. The voltage at sustain electrode X inthe driving waveform of FIG. 10 can be varied as that shown in FIGS. 8and 9.

The voltage which is gradually falling during the reset period has beenapplied to the scan electrode in the first to fourth exemplaryembodiments, and differing from these, floating may be repeatedlyapplied to scan electrode Y during the reset period, which will bedescribed in detail referring to FIG. 11.

FIG. 11 shows a PDP driving waveform diagram according to a fifthexemplary embodiment of the present invention.

As shown, the falling waveform applied to scan electrode Y during thereset period repeatedly reduces a voltage by a predetermined level andfloats scan electrode Y for a predetermined time in the driving waveformaccording to the fifth exemplary embodiment. That is, an operation forreducing the voltage applied to scan electrode Y by a predeterminedlevel of voltage, and intercepting the voltage supplied to scanelectrode Y to thus float scan electrode Y is repeated.

When a discharge is generated in the discharge cell by the voltageapplied to the scan electrode while the operation is repeated, the wallcharges formed in the discharge cell are erased. When scan electrode Yis floated after the discharge is fired, the voltage within thedischarge cell is abruptly reduced to quench the discharge when a smallamount of wall charges within the discharge cell are erased. When thevoltage at scan electrode Y is reduced by a predetermined level ofvoltage, the discharge is fired, and when scan electrode Y is floatedafter the discharge is fired, the voltage within the discharge cell isabruptly reduced to quench the discharge, and accordingly, the smallamount of the wall charges are erased. That is, the erased amount of thewall charges can be precisely controlled.

The wall charges within the discharge cell are erased by a small amountand controlled in the desired manner by repeatedly applying a fallingvoltage to scan electrode Y and floating the electrode as describedabove. That is, the wall charges are precisely erased by repeating theoperation for erasing the wall charges by a small amount.

A strong discharge quench by the floating will be described referring toFIGS. 12A to 12D with reference to sustain electrode X and scanelectrode Y in the discharge cell since the discharge is generatedbetween sustain electrode X and scan electrode Y.

FIG. 12A shows a diagram of modeled discharge cells formed by thesustain electrode and the scan electrode. FIG. 12B shows an equivalentcircuit diagram of FIG. 12A. FIG. 12C shows a state in which an externalvoltage is applied to the discharge cells of FIG. 12A. FIG. 12D shows afloated state when the discharge cells are discharged. For ease ofdescription, it is defined in FIG. 12A that charges −σ_(w) and +σ_(w)are formed on scan electrode 4 and sustain electrode 5 in the earlierstage. The charges are actually formed on the dielectric layer, but theyare described to be formed on the electrodes for ease of description.

As shown in FIG. 12A, scan electrode 4 is coupled to external appliedvoltage V_(h) through a switch SW, and sustain electrode 5 is coupled tovoltage V_(h). Dielectric layer 2 is formed in scan electrode 4 andsustain electrode 5. Discharge gas (not illustrated) is provided betweendielectric layers 2, and the space between the dielectric layers 2 formdischarge space 11.

In this instance, scan electrode 4, sustain electrode 5, dielectriclayers 2, and discharge space 11 can be given as panel capacitor Cp, asshown in FIG. 12B since they form a capacitive load. The dielectricconstant of the two dielectric layers 2 is defined as ∈_(r). The voltagein discharge space 11 is given as V_(g). The thickness of dielectriclayers 2 is established to be the same, and the distance (distance ofthe discharge space) between the two dielectric layers 2 is set to bed₂.

Referring to FIG. 12C, voltage V_(g1) within the discharge space whenswitch SW is turned on, and external voltage V_(in) is applied to scanelectrode 4 is calculated, assuming that charges −σ_(w) and +σ_(w) areapplied to scan electrode 4 and sustain electrode 5 by the externalapplied voltage. Electric field E1 within dielectric layer 2 andelectric field E2 within discharge space 11 are given in Equations 1 and2 by applying the Gaussian law.

$\begin{matrix}{E_{1} = \frac{\sigma_{t}}{ɛ_{r}ɛ_{0}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

where ∈₀ is a permittivity within the discharge space.

$\begin{matrix}{E_{2} = \frac{\sigma_{t} + \sigma_{w}}{ɛ_{0}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

Voltage (V_(e)-V_(in)) applied to an external side is given as Equation3 by the relation of the electric field vs. the distance, and thevoltage within the discharge space is given as Equation 4 from Equations1 to 3.

$\begin{matrix}{{{2\; d_{1}E_{1}} + {d_{2}E_{2}}} = {V_{h} - V_{in}}} & {{Equation}\mspace{14mu} 3} \\{V_{g\; 1} = {{d_{2}E_{2}} = {{{\frac{ɛ_{r}d_{2}}{{ɛ_{r}d_{2}} + {2\; d_{1}}}( {V_{h} - V_{in} - V_{w}} )} + V_{w}} = {{\alpha ( {V_{h} - V_{in}} )} + {( {1 - \alpha} )V_{w}}}}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

where V_(w) is a voltage, given as

${\frac{d_{2}}{ɛ_{0}}\sigma_{w}},$

formed by wall charges σ_(w) within discharge space 11, and α is givenas

$\frac{ɛ_{r}d_{2}}{{ɛ_{r}d_{2}} + {2\; d_{1}}}.$

Next, a discharge is generated between scan electrode 4 and sustainelectrode 5 by voltage V_(in) externally applied to scan electrode 4. Asshown in FIG. 12D, the wall charges formed on scan electrode 4 andsustain electrode 5 are quenched by the amount of σ_(w)′ by thedischarge, switch SW is turned off, and scan electrode 4 is floated.

The charges applied to scan electrode 4 and sustain electrode 5 aremaintained at −σ_(t) and +σ_(t) since no charges are externally appliedin the floated state. In this instance, electric field E1 withindielectric layer 2 and electric field E2 within discharge space 11 aregiven in Equations 1 and 2 by applying the Gaussian law.

$\begin{matrix}{E_{2} = \frac{\sigma_{t} + \sigma_{w} - \sigma_{w}^{\prime}}{ɛ_{0}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

Calculation of voltage V_(g2) within the discharge space from Equations4 and 5 produces Equation 6.

$\begin{matrix}{V_{g\; 2} = {{d_{2}E_{2}} = {{\alpha ( {V_{h} - V_{in}} )} + {( {1 - \alpha} )V_{w}} - {\frac{d_{2}}{ɛ_{0}}\sigma_{w}^{\prime}}}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

As can be determined from Equation 6, the voltage is dropped by thequenched wall charges when switch SW is turned off (is floated). As aresult, since the voltage within discharge space 11 is steeply reducedin the floated state when a small amount of wall charges are quenched,the voltage between the electrodes becomes less than the dischargefiring voltage, and the discharge is steeply quenched.

As described in the fifth exemplary embodiment, the wall charges areprecisely controlled by applying a falling waveform which repeatsapplying of the voltage and floating to scan electrode Y during thereset period. As a result, minute control of the wall charges ispossible since the discharge is quenched by erasing the wall chargeswhich are very much less than the conventional amount. The resettingcaused by the continuously falling ramp waveform makes the voltageapplied to the discharge space gradually fall through a constant voltagevariation to thereby prevent the strong discharge and control the wallcharges. Since the above-noted ramp voltage controls the intensity ofthe discharge by the gradients of the ramp, the resetting time isincreased because restricted conditions of the ramp voltage gradientsfor controlling the wall charges is very difficult. However, theresetting of using the floating as described in the fifth embodimentreduces the resetting time since it uses a voltage dropping principlefor the intensity of the discharge according to erasure of the wallcharges.

The amount of the wall charges quenched on address electrode A isreduced by applying voltage V_(e) to sustain electrode Y after applyingvoltage V_(h) thereto while the falling waveform is applied to scanelectrode Y in the fifth exemplary embodiment in the same manner as thefirst to fourth exemplary embodiments.

As shown in FIGS. 4, 8, 9, 10, and 11 according to the first to fifthexemplary embodiments of the present invention, sustain electrode X inaddress period P_(a) is biased with the same voltage as voltage V_(e) atsustain electrode X in second period P_(r32) of falling period P_(r3),and in addition to this, the voltage at sustain voltage X in addressperiod P_(a) can be established to be greater than voltage V_(e) atsustain electrode X, which will be described with reference to FIG. 13.

FIG. 13 shows a PDP driving waveform diagram according to a sixthexemplary embodiment of the present invention. As shown, the drivingwaveform according to the sixth exemplary embodiment has the samepattern as that of FIG. 4 except for the voltage at sustain electrode Xin address period P_(a). In more detail, a voltage which is greater thanvoltage V_(e) applied to sustain electrode X in second period P_(r32) offalling period P_(r3) is applied to sustain electrode X in addressperiod P_(a). The voltage is illustrated in FIG. 13 to correspond tovoltage V_(h) applied to sustain electrode X in first period P_(r31) offalling period P_(r3). As a result, there is no need to add a powersource for supplying a voltage greater than voltage V_(e).

When voltage V_(h) is applied to sustain electrode X in the case wherevoltage V_(sc) is sequentially applied to scan electrode Y in addressperiod P_(a), the voltage (which includes a wall voltage caused by thewall charges) of between sustain electrode X and scan electrode Y whenvoltage V_(n) is applied to scan electrode Y in address period P_(a)becomes greater than the voltage (which includes a wall voltage causedby the wall charges) between sustain electrode X and scan electrode Y inthe final state of falling period P_(r3). Since the voltage which isgreater than the voltage established in reset period P is appliedbetween sustain electrode X and scan electrode Y, the address dischargeis stably generated.

Further, the voltage at sustain electrode X described referring to FIG.13 can be applicable to the driving waveforms of FIGS. 8 to 11.

Voltage V_(h) used through the first to sixth exemplary embodiments maybe a voltage with the same level as that of voltage VS applied to scanelectrode X and sustain electrode X in sustain period P_(s), and thereis no need to add a power source for supplying voltage V_(h) in thiscase.

According to embodiments of the present invention, the quenched amountof the wall charges on the address electrode during the reset period isreduced, and hence, the voltage applied to the address electrode duringthe address period is reduced.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. (canceled)
 2. A method of driving a plasma display device including ascan electrode and a sustain electrode, the method comprising: graduallyreducing a voltage at the scan electrode from a first voltage to asecond voltage lower than the first voltage, during a falling period ofa reset period; and gradually reducing a voltage at the sustainelectrode from a third voltage to a fourth voltage lower than the thirdvoltage, during at least part of the falling period.
 3. The method ofclaim 2, further comprising gradually increasing the voltage at the scanelectrode from a fifth voltage to a sixth voltage higher than the fifthvoltage, during a rising period of the reset period.
 4. The method ofclaim 3, further comprising applying a seventh voltage to the sustainelectrode during the rising period.
 5. The method of claim 2, whereingradually reducing the voltage at the scan electrode comprises reducingthe voltage at the scan electrode in a ramp format, and graduallyreducing the voltage at the sustain electrode comprises reducing thevoltage at the sustain electrode in the ramp format.
 6. A plasma displaydevice comprising: a scan electrode; a sustain electrode; and a driverfor gradually increasing a voltage at the scan electrode in a risingperiod of a reset period, for gradually reducing the voltage at the scanelectrode in a falling period of the reset period, and for graduallyreducing a voltage at the sustain electrode in the falling period. 7.The plasma display device of claim 6, wherein a period in which thevoltage at the scan electrode is gradually reduced is overlapped with aperiod which the voltage at the sustain electrode is gradually reduced.8. The plasma display device of claim 6, wherein the driver applies apredetermined voltage to the sustain electrode while the voltage at thescan electrode is gradually increased.
 9. The plasma display device ofclaim 6, wherein the driver gradually reduces the voltage at the scanelectrode in a ramp format, and gradually reduces the voltage at thesustain electrode in the ramp format.
 10. A device for driving a plasmadisplay panel including a scan electrode and a sustain electrode, thedevice comprising: a first driver for gradually reducing a voltage atthe scan electrode from a first voltage to a second voltage lower thanthe first voltage, in a falling period of a reset period; and a seconddriver for gradually reducing a voltage at the sustain electrode from athird voltage to a fourth voltage lower than the third voltage, in atleast part of the falling period.
 11. The device of claim 10, whereinthe first driver gradually increases the voltage at the scan electrodefrom a fifth voltage to a sixth voltage higher than the fifth voltage,in a rising period of the reset period.
 12. The device of claim 11,wherein the second driver applies a seventh voltage to the sustainelectrode in the rising period.
 13. The device of claim 10, wherein thefirst driver gradually reduces the voltage at the scan electrode in aramp format, and the second driver gradually reduces the voltage at thesustain electrode in the ramp format.